The present invention relates generally to a fluid containment and delivery vessel. More particularly, the present invention relates to a vessel with optimized flow of a purge gas and a method of using same.
Large vessels, typically cylindrical in shape, are used for the bulk storage and transportation of a fluid. The term “fluid” as used herein denotes liquid as well as gaseous substances. During transportation of relatively large volumes of fluid such as by tractor-trailer or rail car, the fluid within the vessel may tend to slosh forward and aft. This sloshing movement can result in instability within the load and may ultimately lead to rollover of the vessel and/or transportation vehicle, potentially leading to damage to person and property. Further, the continual sloshing movement of the liquid within the vessel can damage the vessel by putting pressure on its welds and joints.
To reduce the destabilization caused by the movement of fluids within the vessel, the vessel may be filled to capacity. This oftentimes may not be possible nor desirable. Further, the Department of Transportation (DOT) regulation 49 CFR Section 173.32(f)(iii)(5) limits the filling of bulk transportation vessels to a filling density of not more than 20% and less than 80% by volume. This filling restriction, however, does not apply if the vessel has dividers that apportion the vessel into compartments of not more than 1,980 gallons capacity.
Dividers, also referred to as baffles, partitions, or surge plates, are used to reduce sloshing of the fluid within the vessel and provide increased stability. Dividers are typically secured at right angles to the anticipated movement of fluids within the tank. Such dividers generally form smaller compartments within the vessel that limit the distance that the liquid can slosh within the tank. Some examples of vessels that contain these types of dividers are described in U.S. Pat. Nos. 1,909,734, 2,011,161, and 4,251,005. U.S. Pat. No. 4,789,170 describes circular shaped, disc baffles that are secured within a tank on a water truck that are designed to attenuate forces directed at them.
One drawback to the use of dividers within bulk fluid storage and delivery vessels is the difficulty in cleaning the interior of the vessel from contaminants prior to use. This step is particularly important when the vessel is used to carry and store high purity (HP) or ultra high purity (UHP) products used for example, in food products, electronics manufacturing, or biomedical applications. The dividers within the tank create “dead zones” or stagnant areas that make it difficult to efficiently remove the contaminants from the internal surface and volume of the vessel. The vessels are typically cleaned through a cycle purge with vacuum application. Vacuum application, however, is not without its drawbacks. Application of vacuum requires structural reinforcement of the vessel walls, which can lead to escalation of the vessel cost. Wall reinforcement can also increase the weight of the vessel, which limits the quantity of product that can be transported. Further, additional equipment, such as vacuum pumps, special valves, and the like need to be available to prepare the vessel prior to use. This additional equipment ultimately increases the operating costs of the vessel. Moreover, there may be an added risk of contaminant entrainment when employing vacuum purging.
Accordingly, there is a need in the art to provide improved vessels to transport and store bulk quantities of a fluid that minimizes the dynamic movement or sloshing of the fluid contained therein. There is a need in the art for vessels and methods using same that eliminate contamination of the fluid contained therein due to inadequate internal surface preparation. There is a need in the art for vessels and methods using same that allow for continuous purging of the internal volume of the vessel. Further, there is a need in the art to minimize the weight of the vessel to ensure maximum product load. Moreover, there is a need in the art to minimize vessel operating costs to ensure competitive product pricing on the market and to ensure maximum revenue.
All references cited herein are incorporated herein by reference in their entirety.